"Blue Dawg" wrote
http://www.cebik.com/quad/quad2.html

why is a reflector using a capacitor a tad bit better on
gain/rejection
on a quad?

==================================
Because the loading capacitor requires a tad bit greater length of the
loaded element which, for the same frequency, slightly changes the
radiation pattern.

When a loading coil is used the element is a tad bit shorter and,
combined with the small loss in the loading coil, it has the opposite
effect.
----
Reg.